We propose to synthesize and to characterize chemically and toxicologically a small group of water soluble vicinal dithiols. We will then determine their relative efficacy as antidotes for acute mercuric chloride poisoning in mice. These compounds include 2,3 dimercaptopropionic acid, 2,3 dimercaptobutanoic acid, and 2,3 dimercaptobutane, 1,4-diol. (The animal tests on these compounds will be carried out on mice given HgCl2 i.p.) We will continue our synthetic efforts to develop compounds which will equal or exceed the antidotal efficacy towards methyl mercuric chloride of the compound reported on this year (DCSA). (The animal tests on these compounds will be carried out on mice receiving CH3HgCl orally.) We will also try to develop an empirical pattern relating the chemical structures of chelating agents to their relative antidotal efficacy for acute mercuric chloride intoxication. This it is hoped, will not only serve as a guide for our synthetic efforts in the preparation of chelating agents of optimum efficacy for mercury, but may well serve also as a pattern which can be related to other toxic heavy metals.